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  • 11
    Electronic Resource
    Electronic Resource
    Some implications of accurate thermal parameters for beryllium (1981)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 848-850 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Authoritative values for the parameters of harmonic thermal motion have been used as criteria for various least-squares refinements of the structure model for beryllium metal. A change in the absolute scale of Brown [Philos. Mag. (1972), 26, 1377-1394] improves the correspondence of the associated data with the true thermal parameters. Contraction of the core-electron distribution upon bonding is a possible implication of the rescaled data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S056773948100185X
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  • 12
    Electronic Resource
    Electronic Resource
    Entropy on charge density: making the quantum mechanical connection (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 86-89 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Entropy maximization has proven effective in treating certain aspects of the phase problem of X-ray diffraction. Much of its development has been expressed in probabilistic language, although image enhancement has been somewhat more physical or geometric in description. Here phasing and entropy maximization are embedded in the quantum mechanical problem of reconstructing an electronic one-matrix under experimental constraints. Entropy on an N-representable one-particle density matrix is well defined. The entropy is the expected form, and it is a simple function of the one-matrix eigenvalues which all must be non-negative. Certain other properties are pertinent to phasing which is implicit in one-matrix reconstruction governed by entropy maximization. Throughout this work reference is made to informational entropy, not the entropy of thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992009429
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  • 13
    Electronic Resource
    Electronic Resource
    Electron density: an exponential model (1983)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 252-256 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Electron density ideally is positive definite. The imperfect experimental data of an X-ray diffraction experiment do not lead to such a function when the density is obtained from structure factors by the linear relationship of Fourier transformation. At the price of certain but quite small bias, electron density may be represented by an otherwise completely general exponential model. The model is based on iterative correction of a logarithm which yields a density approximation of resolution substantially higher than that afforded by Fourier transformation of structure factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767383000537
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  • 14
    Electronic Resource
    Electronic Resource
    Programs for phasing by entropy maximization as implemented in Xtal3.2: a crystallographic software system (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 100-106 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Xtal3.2, a crystallographic software package, is an international development project involving about 40 researchers over a full spectrum of crystallographic interests. This development has been supported by many national and international agencies and commercial institutions since the first version in 1983. The 1992 release, Xtal3.2, contains software for 95 different calculations. These range from the processing of raw diffraction data to interactive molecular graphics, atomic charge estimation, electronic publication preparation, and the structure solution and refinement of small and large molecules. Tests of the Xtal programs for phase determination and phase refinement by the application of `maximum entropy' are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992008898
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  • 15
    Electronic Resource
    Electronic Resource
    Symmetry of density functions based on the n-tuple phase angle (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 405-407 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: With respect to Q({\bar r}, the Fourier transform of the function F_mhF_nh, m 〉 n ≥ 0, (a) possesses the identical lattice and (b) possesses in its factor group identical rotations but translations multiplied by (m - n); In particular, the symmetry of the density function based on 2φ is given by the original elements with factor-group translations doubled. For the special case m = n 〉 0, as required, the density function has the appropriate Laue symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475000952
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  • 16
    Electronic Resource
    Electronic Resource
    Extrapolative filtering. I. Maximization of resolution for one-dimensional positive density functions (1978)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 533-541 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A one-dimensional formalism based on extrapolative filtering can lead to electron-density maps at more than twice the resolution displayed by maps obtained by straightforward Fourier synthesis of structure factors. A worked example illustrates the computations for a hypothetical one-dimensional structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S056773947800114X
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  • 17
    Electronic Resource
    Electronic Resource
    Information theory as a basis for the maximum determinant (1982)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 129-132 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The concepts of information theory have been applied to the analysis of spatial array data in the maximum entropy method. The development is similar to that of Tsoucaris's maximum determinant method for phase determination. It is shown that a maximum determinant (of structure factors) corresponds exactly to a function of maximum entropy. The squared modulus of its Fourier transform formally approximates the true electron density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739482000230
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  • 18
    Electronic Resource
    Electronic Resource
    Extrapolative filtering. II. Formalism for a maximum-entropy enhancement of resolution in n dimensions (1983)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 777-783 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: An extrapolative filtering formalism is used to determine a high-resolution positive-definite density estimator. In an example, comparison with results from Fourier transformation of structure factors shows a resolution enhancement factor of 1.3 for the density estimator. The density estimator satisfies a maximum-entropy criterion and is the direct-space representation of a maximum determinant of structure factors as used in phase determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767383001543
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  • 19
    Electronic Resource
    Electronic Resource
    Scaling by entropy maximization (1984)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 40 (1984), S. 705-708 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Entropy maximization is an alternative to least-squares or squares minimization for the relative scaling of intersecting data sets. The iterative calculations converge rapidly, even for difficult cases, and the scaling is truly relative in contrast-to that of other widely used methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767384001458
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  • 20
    Electronic Resource
    Electronic Resource
    Identification of Meat from Game and Domestic Species (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 57 (1992), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isoelectric focusing combined with specific enzyme staining for creatine kinase was used to characterize banding patterns in meat from pronghorn, mule deer, white-tailed deer, sheep, moose, pork, bison, elk, caribou, red deer, beef and goat. Processed and cooked pork was differentiated from all species and beef and elk were separated from pronghorn. It was not possible to differentiate beef from elk, or prong-horn from sheep. The inability to separate some game from some domestic species and the lability of the staining proteins after heating above 67°C limits the application of this technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1992.tb05529.x
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